Device for coating moving webs of paper or board

ABSTRACT

The invention relates to a coating device for coating moving webs of material, more particularly webs of paper or board, comprising a belt or hose (7), which is trained about the curved guide surface of a beam- or rod-like support member (1) and a drive roll (6), a cooperating roll (C) carrying the web, a coating gap (9) being defined between the cooperating roll (C) and the hose (7) for the application of the coating material to the web or the roll, a support beam (3), which extends in parallelism to the roll and the drive roll (6), for supporting the support member (1), and between the same a pressure hose (4) for the transmission of the support forces. The invention is characterized in that the support member (1) possesses a rib- or rail-like extension in its part remote from the curved guide surface at the gap (9), on which there acts a further pressure hose (5 and 5&#39;) arranged between a corresponding support surface on the support beam (3) and the extension of the support member (1), essentially in a direction which is transverse in relation to the direction of action of the first pressure hose (4 and 4&#39;), the first pressure hose (4 and 4&#39;) being arranged essentially at the free end of the extension (2 and 2&#39;) of the support member (1 and 1&#39;).

The invention relates to a coating device for coating a paper web, orthe like web of material, and particularly to a belt coater and to thesupport for the belt at the coating nip or gap. The coating belt istrained around a curved guide surface of a support, the guide surfacebeing at the coating gap. The support is supported on a rail. Pressuremeans, like a hose, between the support and the rail keeps the guidesurface at a preferred orientation.

German patent publication DE 41 00 771 A1 discloses such a device. Inthis case, the pressure hose serves to compensate for bending or toadjust the bend for the support member with the curved guide surface.Variations in hydrodynamic forces, occurring along the web, on thesupport member in the course of the coating operation however thesupport member to bend so that equalization of such flexure isnecessary.

This object of equalizing such flexure is to be attained with theinvention. The coating device of the invention is used for coatingmoving webs of material, more particularly webs of paper or board. Anendless belt is trained to pass over a curved guide surface of a beam orrod-like support member. A drive roll drives the belt to move over thecurved guide surface. A cooperating web supporting roll supports the webnear to the belt at the curved guide surface to define a coating gapbetween them. A support beam extends parallel to the web supporting rolland supports the support member. First pressure means are disposedbetween the support member and the beam to apply force to the supportmember in a direction toward the coating gap and the web supportingroll. Second pressure means are disposed at the one side of the supportmember and at the support beam as to apply a force essentially in adirection transverse to the direction of force applied by the firstpressure means and also opposing the force applied on the support memberby the belt moving through the coating gap and applying coating on theguide surface. The first and second pressure means may be pressure hosesor other pressure applying means such as piezo translators, hydraulicpistons operating in pressure cylinders, thermally or magneticallydriven servo elements. The drive means for the belt comprises one driveroll in the belt which has a diameter and radius of curvaturesignificantly larger than the radius of curvature of the curved guidesurface.

In order to aid in relative shifting of the support member, particularlywith reference to the second pressure means, the second pressure means,such as a pressure hose, is in contact with an intermediate memberdisposed between the second pressure means and the support member. Theintermediate member and the extension of the support member are mutuallysmooth and slidable with respect to each other to absorb relativesliding motion of the support member with respect to the support beam.

It is an advantage if only one single drive roll is provided for thebelt or, respectively, for the hose, because then the radius ofcurvature of the guide surface of the support member may be designed tobe relatively small, something which is very desirable. It isfurthermore possible to have two guide or drive rolls for the hose, thediameter of such rolls being able to be 400 and 900 mm. It is thennaturally possible for the curvature radius of the guide surface of thesupport member not to be so small.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows the invention will be described with reference to thefigures which illustrate preferred embodiments; the FIGS. 1 and 2 arediagrammatic cross sections taken through the coating device and,respectively, on a larger scale through another working embodiment.

As shown in FIG. 1 the rail- or beam-like support member 1 is arrangedto be parallel to a cooperating roll C on which the web travels throughthe coating gap or nip. The member 1 is supported by a beam 3 which isbeneath and parallel to the support member 1, such supporting action isfirst achieved by a pressure hose 4 arranged at the end of a rib- orrail-like downward extension 2 of the support member 1. At a coating gapor nip 9 defined by the curved end of the support member and thecooperating roll the support member 1 possesses a curved guide surfacefor an endless loop coating belt or hose 7. The belt is trained around adrive roll 6. The diameter of this drive roll preferably amounts tobetween 400 and 900 mm and the radius of the guide surface of thesupport member 1 may be between 40 and 150 mm. On the rib-like extension2 of the support member 1 there acts a further pressure hose 5, suchaction being transverse in relation to the line of action of the firstpressure hose 4. Further, the further pressure hose is on the side ofthe extension 2 that is downstream of the web movement to oppose thedownstream direction force on the support member 1. Accordingly thebending of the support member 1 may be altered and if necessary adjustedor equalized both in the vertical and in the horizontal direction by thepressure hoses 4 and 5, respectively.

Instead of such pressure hose it is furthermore possible to havesuitable rows of piezotranslators or of thrust pistons running inpressure cylinders. One manufacturer of such piezotranslators is thecompany PI Physik Instrumente GmbH, of Siemensstrasse, 76337 Waldbronn,Germany.

Coating is performed using the belt or the hose 7, which is drawnthrough a trough 12 containing the coating material (in liquid form).

As shown in FIG. 2 between the additional hose 5' and the rail-likeextension 2' of the support member 1' an intermediate plate 8 isarranged. Providing that the contact surfaces of the extension 2' andthe intermediate plate 8 are given a very smooth finish, there will onlybe a slight hinderance of the shaping, to be obtained owing to thepressure hose 5', of the support member 1', caused by material of thepressure hose 5', which in certain circumstances may have a relativelyhigh coefficient of friction. This intermediate member may also beemployed to reduce the area moment of inertia of the rail-like extension2 or, respectively, 2' in order to minimize the bending forces whichhave to be produced by the pressure hose 4 or, respectively, 4'. Thisintermediate plate 8 is held at its two end edges, which are illustratedin the figure, by projections in a freely movable fashion on the supportbeam 3'.

Owing to the employment of a second pressure element, whose force ispractically exerted transversely in relation to that of the firstpressure element, it is also possible to compensate for the additionalbending of the support member 1, which results owing to the variationsin hydrodynamic pressure in the course of the coating operation.

I claim:
 1. A coating device for coating a moving web of materialcomprisinga web support roll for supporting a web to be coated; asupport member extending parallel to the web support roll; the supportmember including a curved guide surface extending toward the supportroll; a coating belt in sliding contact with said curved guide surfaceof said support member; means for driving the belt to slide around thecurved guide surface in a moving direction and for tightening the beltover the guide surface as the belt moves thereover; the guide surfacebeing spaced from the web support roll to define a coating gap betweenthe belt and the web wherein coating material travelling on the belt isbrought to coat the web moving past on the web support roll in thecoating gap; a beam for supporting the support member and also extendingparallel to the web support roll; first pressure means disposed betweenthe support member and the beam and positioned for opposing force on thesupport member directed away from the web supporting roll; the supportmember having an extension extending away from the curved guide surfaceand the web support roll; second pressure means disposed between theextension and the beam at a side of the extension of the support memberso as to oppose movement of the support member generally in a directiontransverse to the direction of force applied by the first pressuremeans.
 2. The coating device of claim 1, wherein the first pressuremeans comprises a first pressure hose disposed between the supportmember and the beam, andthe second pressure means comprises a secondpressure hose disposed between the support member and the beam such thatwhen the first and second hoses are pressurized, they exert greaterpressure on the support member in their respective directions of forceapplication.
 3. The coating device of claim 1, wherein the extension ofthe support member has a free end away from the curved guide surface ofthe support member; and the first pressure means is disposed between thesupport member and the support beam at the free end of the extension ofthe support member.
 4. The coating device of claim 3, wherein theextension is a rail-like extension away from the curved guide surfaceand from the web supporting roll.
 5. The coating device of claim 4,wherein the support beam includes a first surface which extendsgenerally across the direction that is away from the web supporting rolland away from the guide surface, and the first pressure means isdisposed at the first surface; anda second surface transverse to thefirst surface and extending in the direction away from the web supportroll and the guide surface and the second pressure means is disposed atthe second surface.
 6. The coating device of claim 4, wherein the firstpressure means comprises a first pressure hose disposed between thesupport member and the beam, andthe second pressure means comprises asecond pressure hose disposed between the support member and the beamsuch that when the first and second hoses are pressurized, they exertgreater pressure on the support member in their respective directions offorce application.
 7. The coating device of claim 6, further comprisinga rail-like intermediate member disposed between the second pressurehose and the extension of the support member, and the intermediatemember is supported to extend parallel to the second pressure hose andto be free movable with respect to the beam, the intermediate member andthe extension of the support member being in contact with each other byrespective smooth and relatively slidable mutual contact surfacesthereon.
 8. The coating device of claim 1, wherein the means for drivingthe belt comprises a rotatable drive roll in engagement with the beltand rotatable for moving the belt to bring coating material to thecoating gap.
 9. The coating device of claim 8, wherein there is a singleone of the drive rolls for the coating belt.
 10. The coating device ofclaim 9, wherein the drive roll has a diameter in the range between 400and 900 mm; and the curved guide surface of the support member has aradius of curvature that is in the range of 10 to 150 mm.
 11. Thecoating device of claim 10, wherein the guide surface of the supportmember has a radius of curvature in the range of 20 to 80 mm.
 12. Thecoating device of claim 1, wherein the first and second pressure meansare selected from the group consisting of piezo translators, hydraulicpistons and respective pressure cylinders, and thermally driven servoelements and magnetically driven servo elements.